There exists in the pelletizing art three types of pelletizing devices each designed to provide a somewhat different pellet size and size distribution. Each has its relative advantages considering the type of material being pelletized. More specifically, there exist shallow pan or disc type pelletizers, deep pan pelletizers and deep drum pelletizers. For example, a shallow disc pelletizer might have a depth to diameter ratio of 0.1 to 0.3, a deep pan pelletizer a depth to diameter ratio of 0.3 to 0.5 and a deep drum pelletizer a depth to diameter ratio of 0.5 to 0.7. It is generally desirable to be able to experiment with varying types of pelletizers in the laboratory before moving to a large production device. In this way, the most suitable pelletizer for a given application may be determined on a small scale.
It is an advantage according to this invention to provide a pelletizer having an adjustable depth to diameter ratio.